Lenz, O. K. ; Wilde, V. ; Riegel, W. ; Harms, F.-J. (2010)
A 600 k.y. record of El Niño–Southern Oscillation (ENSO) from Lake Messel, Germany: Annual algal blooms as evidence for persisting teleconnections during the Middle Eocene of Central Europe.
8th European Palaeobotany - Palynology Conference 2010. Budapest (6.-10. Juli 2010)
Konferenzveröffentlichung, Bibliographie

Kurzbeschreibung (Abstract)

The oil-shale of the Middle Eocene Lake Messel is one of the world’s best known fossillagerstätten. A continuous core from the center of the basin in 2001 proved that the oil shale was deposited in a meromictic maar lake which formed due to a phreatomagmatic eruption dated as 47.8 Ma. The new drill core includes a complete reference section of the Middle Eocene lake deposits representing a unique climate archive for the Middle Eocene in Central Europe. The classical “Messel oil-shale” of the Middle Messel Formation is characterized by a continuous succession of finely laminated bituminous claystones, representing long-term stable meromictic conditions. They show a very fine light and dark lamination, which is the product of annual algal blooms of the coccal green alga Tetraedron minimum. Therefore, the oil shale is made up of light spring and summer layers caused by algal blooms that were superimposed on the terrigenous background sedimentation, as represented by the dark autumn and winter layers. Since varved maar lake deposits have served as accurate archives of climatic changes during the Quaternary, we used the core Messel 2001 to test whether much more subtle changes during the stable greenhouse phase of the Eocene are recorded in the Messel oil shale. Here we show that short-term fluctuations in lacustrine sedimentation are reflected in the varved sediments which can be attributed to a robust Eocene ENSO. Today ENSO is one of the most important factors in global climate dynamics. Low frequency ENSO-like modulations also occur on a geological scale whereby for the Eocene before only a climate model postulated that ENSO in Central Europe was robust during the Eocene hothouse ca. 35–55 Ma. To test this modeled ENSO signals four suitable slices of the Messel Formation were selected from the core in order to count varves. Total varve thickness and the thickness of light and dark laminae were measured by using a software tool. The data were treated with spectral analyses in order to detect possible cyclic fluctuations in varve thickness. Fluctuations are significant in the quasi-biennial (2.1-2.5 yr) and low-frequency band (2.8-3.5 yr, 4.9-5.6 yr) thus showing that algal growth as well as the background sedimentation were controlled by ENSO effects at least over a time interval of 600 k.y. This confirms the existence of the previously postulated robust Eocene ENSO. Significant signals of quasi-decadal (10-12 yr), interdecadal (17-22 yr) and multidecadal fluctuations (~52 yr, ~82 yr) show the enduring influence of more or less cyclic instabilities which are comparable to modern instabilities like the PDO, the Pacific Decadal Oscillation.

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